With ever increasing fuel costs, there is a concerted effort in the railroad industry to increase productivity. Historically, such increases have been achieved by increasing rolling stock in a train consist and additionally the capacity of the rail cars themselves. However, the practical load limit of today's track system has generally been reached so that attention is now being directed in other areas, such as, lightening the weight of rolling stock, which includes the substitution of newer, lighter weight materials where possible without sacrificing strength or unreasonably increasing costs.
In addition, practical train lengths and practical speeds at which train traffic can operate in a relatively safe manner have been reached without improvement in stability and ride quality. Hence, basic equipment designs are being reevaluated not only to lighten weight, but to improve performance, stability and ride quality, such as by reducing slack that has been common in most coupling designs.
Although minor improvements may seem trivial, the over-all benefits to be achieved can be significant, especially when it is realized that in 1994, for example, the North American railroad industry transported about 1.2 trillion ton-miles of lading in a fleet of 1.5 million cars, with an annual revenue of $31 billion. Even as to individual trains, it is apparent that in a train consist made up of 100 cars, a 4-pound reduction per coupler, translates into an 800 pound reduction per train, and a 1/8-inch reduction in slack per coupler will translate into an over-all slack reduction of more than two feet throughout the 100 car train.
In 1932, the Type E coupler was adopted by the ARA, American Railway Association (predecessor to the AAR, Association of American Railroads) as the standard coupler for railway type freight cars. Although modified periodically since then to meet changing requirements imposed by changing demands, and other coupler designs have been developed for special applications, the Type E coupler is today still the standard coupler for freight type service. As the standard coupler, all of the producers of such couplers in the United States are expected to produce the coupler to the standard specification, so that such couplers are completely interchangeable regardless of the manufacturer.
The Type E coupler is well known to those knowledgeable in the trade as having a pivotal, vertical-knuckle adapted to engage a like vertical-knuckle on an adjacent coupler, so that when the couplers are brought into contact with each other, the two knuckles are pivoted into an interlocking, engaging position. Each coupler includes a gravity activated, coupler lock member adapted to slide downwardly after coupler engagement to virtually lock each knuckle at its engaged position.
To permit the coupler to become disengaged, each coupler lock member must be raised within its slide-channel, so that a draft load on the couplers will tend to pull the cars apart which causes the knuckles to pivot away from each other and thereby become disengaged.
The Type E railway coupler further includes a cast steel coupler head at the forward end extending from a shank adapted to be attached to a yoke, which secures the coupler to the railway car. The forward end of the coupler head is generally V-shaped in horizontal cross-section with the above-described vertical-knuckle vertically pinned at one leg of the "V", and adapted to engage an identical vertical-knuckle on an adjacent car, as above-described.
The vertical-knuckle, adapted for pivotal movement about a vertical pin, is generally hook shaped in section, having a front face, a nose, a throat, and a pulling face at the forward end, and an arcuate tail mass at the back end adapted to be pivoted within a mating, arcuate channel within the coupler head along with pivotal movement of the knuckle.
The coupler lock includes a sliding lock member having an exceptionally complex configuration including a leg extending downwardly from a lock-head portion with the lock head portion disposed for vertical sliding motion within a vertical channel within the coupler head, such that the lock-head portion of the lock member, when moved to its lower-most position, will lie in the path of the tail portion of the knuckle, thereby preventing the coupler knuckle from being pivoted to the open position.
Only by slidably repositioning the coupler lock member upwardly, with the head portion moved away from the knuckle, can the knuckle be pivoted to the open position, such that the tail portion of the coupler knuckle will be free to pivot under the lock-head. These and other operating parts of the Type E railway coupler are well known to those persons familiar with the art and have been since 1932, so that a further detailed description is not believed to be necessary here.
It is however noted, that while the lock member is normally used in its as-cast condition, the coupler lock is required by AAR specifications to be manufactured of cast or forged steel to the dimensions illustrated in FIGS. 7-12 of the attached drawings. Because the coupler head, knuckle and lock member are utilized in their as-cast or as-forged condition, the specification tolerances have to assure a sufficiently loose fitting so that the components will function as intended without any binding, and as a result, a considerable degree of slack is naturally incorporated.
While machining to closer tolerances would essentially eliminate a considerable degree of the slack, it should be readily apparent that the rather complicated forms of the three components are such that the cost of machining would be excessive and prohibitive.